Carbon is the most abundant naturally occurring element exhibiting an amazing variety of molecular and structural formulations which find numerous applications in diverse technoiogies. The forms include nanomaterials such as follerenes, nanotubes, graphene, staircase structures, nano-onions, nano-diamonds etc. as well as high surface area layered Configurations, amorphous carbon, porous carbon which can span higher length scales (mesoscopic and microscopic). A number of carbon based composites also find numerous applications in different fields. Such applications are attributable to their interesting mechanical, electrical, thermal, catalytic and optical properties.
These different forms of carbon and carbon based nanocomposites with metals, semiconductors and compounds (oxides, nitrides, carbides etc.) have been generally synthesized by established techniques of carbon synthesis such as carbonization of organic/polymeric precursors, autoclave synthesis from small halogenated aromatic molecules, chemical vapor deposition, excimer laser ablation of graphitic targets, sputtering/plasma methods, arc discharge methods, chemical methods (autoclave) etc.
An article titled “Analysis of photodecomposition of gaseous chlorobenzene by KrF Excimer Laser” by Kunihiko Nakayama et. al in Analytical Sciences, August 2002, Vol. 18 discloses irradiation of gaseous rnonochlorobenzene with KrF excimer laser with a repetition rate of 10 Hz and an high energy fluence of 9.4 mJcm3 under reduced pressure in presence or absence of oxygen to yield carbon dioxide, carbon monoxide, hydrogen chloride, acetylene and benzene and many unidentified products in the solid phase.
An article titled “Laser photolysis of liquid benzene and toluene: Graphitic and polymeric carbon formation at ambient temperature by Pola et al. Carbon 1997, 35, 605 describes a random polymeric/graphitic carbon formation from laser photolysis of benzene and toluene. This process however involves the ArF (193 nm) laser which has higher energy and leads to the breakdown of the aromatic ring as a primary process rather than stitching of the rings.
The methods known for carbon synthesis from the liquid halogen containing aromatic molecules such as halo aromatics, bicyclic rings containing a halogen atom etc. which are toxic in nature and have adverse effect on human health and also has undesirable environmental effects, either require high temperature chemical reactions or involve laser ablation of these liquids in carbon targets.
Thus the technological challenge lies in the synthesis of various carbon forms at low temperature and mild conditions. Furthermore in principle, a complete conversion of liquid materials to solid carbon can be achieved by a cyclic process of solvent irradiation and distillation to recycle the solvent followed by further irradiation. To achieve the desired carbon nanocomposites, the current invention is focused on, hitherto, unexplored use of economical laser photochemistry for photolysis of halogen containing aromatic molecules at low temperature and mild conditions.